Problem: What is the greatest common factor of $9$ and $4$ ? Another way to say this is: $\operatorname{gcf}(9, 4) = {?}$
Solution: The greatest common factor is the largest number that is a factor of both $9$ and $4$ The factors of $9$ are $1$ $3$ , and $9$ The factors of $4$ are $1$ $2$ , and $4$ Thus, the greatest common factor of $9$ and $4$ is $1$. $\operatorname{gcf}(9, 4) = 1$